The word “population” and “populace” are from the same Latin root, which is one of the reasons why they look similar; these words can be used in a context together but with different meanings, which makes it easy to differentiate them.
A population can simply be defined as the total number of people living in a geographical location. To know the total number of people living in that location, you will have to carry out a census. On the other hand, the populace means the inhabitants of a nation; they are mostly considered as normal people. The wealthy or rich and elite are not considered as normal people, because these people are extremely privileged; they are not considered as part of the populace.
There are always some words that will seem confusing in the beginning, especially if you have always assumed that they are the same. The population is known to refer to the number of people that are available in a certain place.
This means that you would need to count the number of people who are living in a specific area. When you say populace, this means that you are referring to people that are considered to be “normal.” Those who are considered to be rich or wealthy will not be considered here. There are some that are extremely privileged, so they cannot be considered a part of the populace.